Maki Aikawa may look like an ordinary high school girl, but she’s actually a street fighter within the dark alleyways and back streets of Tokyo. To date, she remains undefeated against both men and women. And with a unique arsenal of aerial techniques allowing her to knock out opponents at will, people began to call her the Air Master.
Behind the scenes of the hustle and bustle of everyday life in Tokyo, there exist many people who strive to become stronger by competing against each other in street fights. The main protagonist is Maki Aikawa, a 16 year-old high school student. A former gymnast, Maki adapts her skills to a different way of life — street fighting. The only thing that truly makes her feel alive is the rush and pressure experienced while fighting. With amazing power and grace, she fights opponent after opponent, repeatedly demonstrating the gymnastic talent that earns her her street name, "Airmaster". Eventually, Maki is exposed to a fighting league of sorts, known as the Fukamichi Rankings.
The Fukamichi Rankings consist of the world's greatest street fighters and martial artists. The Fukamichi Ranking fights are held for various reasons. Firstly, many fighters wish to test themselves, achieving the highest rank possible and stretching themselves to their physical limits. However, there is also a corporate side to the Fukamichi rankings, with many viewers around the world eager to watch the brutal yet awe-inspiring showdowns. Each Fukamichi ranker is paid a respective amount for winning within their fight. Maki, seeking to quench her thirst for that pressure or buzz she experiences only through fighting and to find her place within this world, scales the Fukamichi Rankings, clashing with the world's greatest fighting prodigies.
- Maki Aikawa Formerly a gymnast who trained under her now-deceased mother, Maki uses her acrobatic skill in her fighting style to increase freedom of movement. Her attacks combine vertiginous leaps and somersaults with the fearsome, furious power of her kicks and throws. Maki has the ability to replicate most nearly any move she gets hit with or sees, and when in combat possesses an awe-inspiring resilience, presence, and strength of will. Since her relationship with her father is conflicted, she lives alone. Maki seems to enjoy street fighting for the 'rush' rather than any sense of revenge or honor. When not fighting, Maki tends to stick out in a crowd due to her unusual height (6 feet, which is very tall for a teen Japanese girl) and appearance, preferring to follow her quartet of friends quietly. Her younger sister comments that Maki is somewhat simpleminded. Maki is reluctant to deal with several people obsessed with her. She becomes vulnerable to attack, for a moment, when she gets approached in any romantic way, especially with Julietta Sakamoto. Her signature moves are the "Air Spin Driver" and the " Air Cutter"; she is later shown to master the art of Air Flow. Maki is voiced by Romi Paku.
- Yuu Takigawa Yuu is a friend of Maki and shares some of the same interest as Renge. She is a fan of the singer Uzumi Mika. She is taking karate lessons and also has a crush on Shinnosuke, and sometimes she fights with Michiru about Shinnosuke. Yuu is voiced by Mariko Suzuki.
- Michiru Kawamoto Michiru is a friend of Maki. She also has a crush on Shinnosuke, but becomes upset when he admits his love for Maki. She is a fan of the model Nono Rakuko. Yuu and Michiru make a great duo and are seldom seen apart. Michiru is voiced by Masumi Asano.
- Mina Nakanotani One of Maki's shier friends, she goes to a presumably rich, private school. Mina has ridiculously exaggerated breasts used normally as a source of humor rather than fan-service, and she is extremely self-conscious about it. Thanks to her large breasts, she is extremely popular with many males characters in the series. In addition to this, Mina is hopelessly in love with Maki (who is not sure how to handle the matter), making this the main reason her friends make fun of her. Mina is voiced by Yukana.
- Renge Inui The group's extremely short friend. Renge has a penchant for eating obsessively, yet she is always thin (sometimes when she eats a lot, she is shown to have a belly). Renge is the stereotypical overexcited kid with a tendency to whine, but she serves as a cheering squad. She later acquires a kitten that she carries with her most of the time. She also has "psychic" powers. Renge is voiced by Tomoko Kaneda.
- Shiro Saeki Maki's estranged father. Maki was born when he was 15, which would make him around 31 years old. He's a four-time pro-fighting champion. He runs a dojo and raises Maki's half-sister, Miori. He gets beaten by Sakamoto, but they become friends later on. Shiro is voiced by Toshio Furukawa.
- Miori Saeki Maki's somewhat bratty younger half-sister. Her martial-artist father is the same as Maki's, so she shares some of her older sister's fighting ability, but none of her gravity-defying gymnastic skill, which Maki evidently got from her mother. In her first appearance, she suddenly attacks Maki. She is about the same height as Renge, though she is younger. She decides to move in with Maki. She later idolizes Sanpagita Kai. Miori is voiced by Yukiko Hirotsu.
- Kaori Sakiyama A wanna-be future model (later a female wrestler) with an obsessive one-sided rivalry with Maki. She later becomes a moderately good fighter, and accomplishes things by sheer force of will and determination. She is loud and over-dramatic, and during extended fights is essentially a Berserker powered by her own rage, and she will not admit defeat unless violently knocked out. A running gag in the show is how most characters refer to her by her full name in a dramatic fashion, probably due to her tendency to do the same. When enraged, her appearance has been compared to the Devilman. Due to a childhood "accident" (really a beatdown by a high school rival), she is deaf in her right ear. Kaori is voiced by Miki Doi.
- Julietta Sakamoto A scruffy but handsome ghost writer who becomes obsessed with Maki (romantically), while the latter is totally uninterested in him and finds his behavior very creepy. He is a smooth talker but prone to overly aggressive declarations of love, sometimes bordering on assault, towards Maki, who he calls "My Jenny". He tends to always kiss her and declare his love for her when they're together, even during their fights, throwing her off balance. This is usually done for comedic effect. He has three women who are head over heels for him: Uzumi Mika (a famous singer), Nono Rakuko (a famous model), and Nanjou Remon (a famous novelist). He ignores them all since he's fixed on marrying Maki and making her move in with him. Maki is physically capable of beating him down in his insane-like "distracted" state of mind ; however, she did have a hard time with him at first. He can take a huge beating and still be able to fight. In a fight with another opponent he once had both his legs and one of his arms broken but he was still able to fight. Sakamoto usually only fights with extremely fast and devastating kicks. He usually leaves his hands in his pockets while fighting even though he has a powerful punch. It's said his strength is legendary on the street. He becomes rank seven in the Fukamichi Rankings after defeating Nobuhiko Fukamichi in a single kick. Julietta is voiced by Kenyu Horiuchi.
- Kinjiro Kitaeda Leader of the League of Black-suited Gentlemen. He claims to hate women yet he likes Maki because he thinks she's different. He's a good fighter and has great punching power. He once took down a bear with one punch. He has a technique where he can create an afterimage of himself attacking so the opponent will be fooled into acting prematurely. He had his first kiss stolen by one of his male subordinates, Nagato the long fist, while Nagato fights Fukamichi. Kinjiro is ranked ninth within the Fukamichi rankings. Kinjiro is voiced by Kentaro Ito.
- Kai Sanpagita Though she is not initially involved in the street-fighting tournament Maki joins, Sampaguita Kai was one of her most difficult opponents. Using a similar fighting style to Maki, Kai faces her in a tag-team match during a women's wrestling tournament. She becomes obsessed, like a number of Maki's earlier opponents, with beating Maki. She's the younger sister of Lucha Master, who taught her how to fight ever since she was young. Kai gained the ninth rank within the Fukamichi Rankings after beating Shun Yashiki, however she is narrowly defeated by Kinjiro Kitaeda, which leaves her ranked ten. Kai's signature moves are the "Izakaya Bomber" and the "Ultimate Sky Screwbomb", the first involves a clothesline takedown and the other is a brainbuster into a spinning sitout powerbomb; she learns the former from her former mentor/wrestling partner Hayase Mio and the latter is of her own creation. Kai is voiced by Michie Ishizuka.
- Shinnosuke Tokita A guy who challenges Maki early on, but later temporarily joins the group. He seems to have a crush on Maki. He fights with a long staff that can separate into three parts connected with a chain. He seems to know the art of the Drunken Fist.
- Lucha Master Lucha Master is, as the name implies, a masterful wrestler, styled after Mexican Luchadores. He always wears a mask, and he is the first major challenge Maki faces. He is one of only three characters who can use a similar sort of aerial combat to Maki. He is the older brother of Sanpaguita Kai, another character with a similar fighting style. Lucha Master is ranked twenty-first within the Fukamichi Rankings. Lucha Master is voiced by Unshō Ishizuka.
- Tsukio Taketsugu Another early opponent. He is a construction worker who has a furious punch similar to a jackhammer, but is not as fast as some of the other street fighters. Maki often overlooks him, especially since, after his first appearance, Lucha Master quickly showed up, and this makes him furious. Tsukio is ranked twenty-second within the Fukamichi rankings. Tsukio is voiced by Kihachiro Uemu.
- Reiichi Mishima A sort of hanger-on to Tsukio Taketsugu, Reiichi is sometimes a coward and a klutz. Though he could only fight well with a bike, using it like it's part of his own body, he's still only a moderately skilled street fighter. He also has a crush on Mina Nakanotani and often fantasizes about being her hero; when faced with the actual necessity of saving her from Kinjiro's mob he fights bravely but is eventually overwhelmed and is forced to yield leadership to stronger fighters. Reiichi is voiced by Daisuke Sakaguchi.
- Fukamichi The man who runs the street fighting tournament, and who gave his name to the ranking system (Fukamichi Rankings). He decides who is qualified to be in the Tournament rankings. He watches the fights and has videos of them streamed to his laptop, which he then broadcasts all over the world on the internet. He does not participate in the fights, but he's been shown to be extremely strong and fast. He has a younger brother (Nobuhiko Fukamichi), who participates in the competition. He has a hobby of critiquing restaurants and posting the results on the internet. In the final episode, Fukamichi reveals that he created the ranks to gather warriors who could defeat Eternal, the 1st ranked fighter.
- Shun Yashiki Tsukio's younger cousin. Originally 9th place in the Fukamichi Tournament, but after losing his rank to Kai, he decided to beat the 8th place holder. He's a ki manipulator. He has a technique where he uses his ki to create an osmotic punch, which strongly pressures the insides of an opponent's body resulting in a loss of a massive amount of liquid within their body, rendering them incapacitated. Since he uses his ki for this technique, he can only use it a certain amount of times until he rests to build up his ki again. He teaches this technique to Kaori Sakiyama.
- Yuki Minaguchi is ranked number four. Her full fighting style emphasizes on counter attacks as well as cutting and stabbing techniques with her hands. She is the first person to ever beat Maki in a fight. She starts her fight as a calm and collected individual, though Maki sees through her and knows that she likes to fight.
- Yoshinori Konishi The 3rd place holder in the Fukamichi Rankings. Konishi believes he has attained perfection and specializes in grappling and submission techniques. He is shown to easily beat Shiro Saeki who is also proficient in submission techniques, and fight on par with and eventually "defeat" Sakamoto Julietta.
- Eternal The 1st place holder in the Fukamichi ranking, he seems to be one of about fourteen before him. Eternal is one of the strongest, if not the strongest, fighters in the world, capable of leveling an entire building in one punch. He is defeated only by the combined efforts of Aikawa Maki and Minaguchi Yuki, whom he decimated in a one-on-one fight. He disappears after the building he and Maki fought in collapses, implying he was either killed by the collapse or simply left the building before Maki.